1. Field of the Invention
The present invention relates to electroluminescent devices employing an organic luminescent material/clay nanocomposite, more specifically, to an organic luminescent material/clay nanocomposite with improved luminescent efficiency and stability, which is prepared by blending an organic luminescent material and a nanoclay, and electroluminescent devices employing the same.
2. Description of the Related Art
The development of electroluminescent (xe2x80x9cELxe2x80x9d) devices that emit light by applying an electric field has been continued, and polymer EL devices employing organic polymer/inorganic material nanocomposites have been developed and practiced in the art. These polymer EL devices utilize semiconductive inorganic materials, such as ZnS and CdS, and insulating inorganic materials such as SiO2 and TiO2. W. Que teaches luminescent polymers employing the semiconductive inorganic material, ZnS, and H. Mattoussi also teaches luminescent polymers employing the semiconductive inorganic material, CdS (see: W. Que, Applied Physics Letter, 73:2727, 1998; H. Mattoussi, Journal of Applied Physics, 83:796, 1998). Besides, luminescent polymers employing an insulating inorganic material of SiO2 have been reported by S. A. Carter, and luminescent polymers employing an insulating inorganic material of TiO2 have been reported by L. Gozano (see: S. A. Carter, Applied Physics Letters, 71:1145, 1997; L. Gozano, Applied Physics Letters, 73:3911, 1998), in which the inorganic materials mixed with polymers have been used as luminescent layers. The inorganic nanomaterials are known to help charge transport. However, the luminescent efficiencies of these newly developed EL devices are not considerably improved compared to the luminescent efficiencies of the conventional devices, and the stability of the devices are low due to the unsolved problem of penetration of oxygen and water.
Therefore, there are strong reasons for developing and exploring a novel material that can solve the problems associated with the polymer EL devices described above.
The present inventors made an effort to provide a material that can improve the luminescent efficiency and stability of EL devices, and discovered that EL devices employing a luminescent material, an organic EL material/clay nanocomposite, prepared by blending an organic EL materials and a nanoclay, show the improved luminescent efficiency and stability.
A primary object of the present invention is, therefore, to provide an organic EL material/clay nanocomposite, prepared by blending an organic EL material and a nanoclay.
The other object of the present invention is to provide EL devices employing the organic EL material/clay nanocomposite.
Accordingly, a preferred embodiment provides a nanocomposite comprising an organic luminescent material and a laminated inorganic material, wherein the laminated inorganic material comprises layered plates and wherein the organic luminescent material is intercalated between the layered plates.
Another preferred embodiment provides an electroluminescent device which comprises: a transparent substrate; a semitransparent electrode deposited on the transparent substrate; an emissive layer comprising a nanocomposite, positioned on the semitransparent electrode; and a metal electrode deposited on the emissive layer.
Another preferred embodiment provides an electroluminescent device which comprises: a transparent substrate; a semitransparent electrode deposited on the transparent substrate; a hole transporting layer positioned on the semitransparent electrode; an emissive layer comprising a nanocomposite, positioned on the hole transporting layer; and a metal electrode deposited on the emissive layer.
Another preferred embodiment provides an electroluminescent device which comprises: a transparent substrate; a semitransparent electrode deposited on the transparent substrate; an emissive layer comprising a nanocomposite, positioned on the semitransparent electrode; an electron transporting layer positioned on the emissive layer; and a metal electrode deposited on the electron transporting layer.
Another preferred embodiment provides an electroluminescent device which comprises: a transparent substrate; a semitransparent electrode deposited on the transparent substrate; a hole transporting layer positioned on the semitransparent electrode, wherein the hole transporting layer comprises a material selected from the group consisting of poly(9-vinylcarbazole), 4,4xe2x80x2-dicarbazolyl-1,1xe2x80x2-biphenyl, (N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-bis-(3-methylphenyl)-1,1xe2x80x2-biphenyl-4,4xe2x80x2-diamine), (4,4xe2x80x2-bis[N-(-naphthyl-1-)-N-phenyl-amino]-biphenyl), triarylamine, pyrazole, and derivatives thereof; an emissive layer comprising the nanocomposite of claim 1, positioned on the hole transporting layer; an electron transporting layer positioned on the emissive layer, wherein the electron transporting layer comprises a material selected from the group consisting of 2,2xe2x80x2,2xe2x80x2-(1,3,5-phenylene-tris[1-phenyl-1H-benzimidazole], poly(phenyl quinoxaline), 1,3,5-tris-[(6,7,-dimethyl-3-phenyl)quinoxaline-2-yl]benzene, polyquinoline, tris(8-hydroxyquinoline)aluminum, and 6-N,N-diethylamino-1-methyl-3-phenyl-1H-pyrazolo[3,4-b]quinoline; and a metal electrode deposited on the electron transporting layer.
These and other embodiments are described in greater detail below.